To achieve slower release for a lipophilic drug in an IM injection, which solvent would slow release?

To achieve slower release for a lipophilic drug in an IM injection, which solvent would slow release?

• A. Oil as solvent would slow release
• B. Water as solvent would slow release
• C. Alcohol as solvent would slow release
• D. Glycerin as solvent would slow release

Answer: (A)

Using an oil-based solvent slows release because the drug remains in the oil phase, forming a depot that must partition into the surrounding aqueous tissue fluids to enter the bloodstream. Lipophilic drugs have a strong affinity for oil, so they are retained in the oil until they slowly diffuse out into interstitial fluid. Water-based solvents dissolve the drug directly into the aqueous environment, leading to faster absorption. Alcohol is miscible with water and tissues, which promotes quicker release as well. Glycerin is viscous and hydrophilic, offering some slowing effect, but not as effectively as oil for keeping a lipophilic drug in a reservoir. Thus, oil as the solvent provides the slowest release for a lipophilic drug in an intramuscular injection.

Using an oil-based solvent slows release because the drug remains in the oil phase, forming a depot that must partition into the surrounding aqueous tissue fluids to enter the bloodstream. Lipophilic drugs have a strong affinity for oil, so they are retained in the oil until they slowly diffuse out into interstitial fluid. Water-based solvents dissolve the drug directly into the aqueous environment, leading to faster absorption. Alcohol is miscible with water and tissues, which promotes quicker release as well. Glycerin is viscous and hydrophilic, offering some slowing effect, but not as effectively as oil for keeping a lipophilic drug in a reservoir. Thus, oil as the solvent provides the slowest release for a lipophilic drug in an intramuscular injection.